The aim of this investigation is to explore the relationship between ventricular rhythm disorders induced by coronary occlusion and adrenergic nervous and adrenal medullary activity with particular emphasis on the time interval immediately following occlusion. For this purpose we intend to (1) explore the relationship between nervous activity in the cardiac accelerator nerves and ventricular rhythm disturbances induced by coronary artery occlusion (2) determine the relative contribution of neural, myogenic and adrenal medullary factors to the genesis of ventricular rhythm disturbances subsequent to coronary artery occlusion and (3) determine the relative importance of drug action on adrenergic nerves, cardiac muscle and secretions from the adrenal medulla in preventing arrhythmias induced by coronary occlusion. To determine the effects of drugs and the adrenergic nervous-adrenal medullary axis on arrhythmias, the action of these procedures on the development of nonuniform activity in adrenergic nerves and in cardiac muscle as well as on the automaticity of ectopic pacemaker tissues will be studied. In vitro and in vivo techniques will be employed.